cpu heatsink

Not sure how to choose the best CPU heatsink? This guide will talk you through everything you need to know before making the purchase.

In the interest of making this article valuable to anyone with the physical dexterity to replace a CPU and/or heatsink, I will impart a basic understanding of the concept.

Much like the human body, the part that uses the most total energy is the part that does the most calculation. In a human it’s the brain, using about 60% of the energy an average person consumes.

In a computer, this load is split between the CPU and the GPU. Most graphics cards come with a more than adequate cooler because replacing one is a tedious job. The CPU heatsink, though, has become a very simple thing to replace and re-seat.

CPU History

The history of CPUs and their thermal properties is interesting… to people like me anyway. Back in the old days the core processors of a Personal Computer (PC) didn’t produce enough heat to even be a problem. Even up to the days of Windows 95, the average 486 CPU didn’t need a heatsink. But as the calculation power increased, so did the power requirements and subsequently the heat output.

The first PC CPU line to usually require a heatsink was the Pentium. Compared to their predecessors they were massively powerful chips. Still it would often be adequately cooled by a two cubic inch block of fluted aluminium or copper.

The Pentium 3 was often on a slot card with a built-in folded heatsink and optional fan. The fans on these were tiny, high speed, and sounded very annoying.

P3 CPU with folded heatsink
The Pentium 3 slot card variant, with folded aluminium heatsink.

In the modern market, the power balance of CPUs has improved, with most consumer chips sipping power like tea at a fancy party. They don’t create a lot of heat unless they’re actively doing something.

But in exchange for this efficiency at idle, the temperature difference under load is much greater. As such, a fluted block of aluminium isn’t enough for most CPUs anymore.

What you’ll be buying

Enter heat pipes. The heat pipe heatsink relies on the properties of evaporation and condensation. A copper tube is filled with an evaporative liquid coolant and sealed at both ends. Then a series of fins is attached to remove heat from the pipes and send it off into the air. The liquid condenses and makes its way back to the heat source where the cycle begins again.

ADEO Heatpipe
Types of Heatpipe
Source – ADEO Heatpipe

Early heat pipes were merely fluted inside, and often contained drug store rubbing alcohol or even distilled water. Modern heatsinks usually contain a specific grade of alcohol or an artificial alternative with specific thermal properties. And the best ones now use a wicking mesh or metal sponge lining to help the process along.

The latest innovation is actually a hybrid of the old and new. A vapour chamber is a self-contained evaporative system that works on the same principle as a heat pipe. Typically the base is a very small heatsink with very small fins within the slightly larger chamber. The chamber passes the heat from the contact surface outwards to the other surfaces. From there it goes to a more standard heatsink.

Vapour chamber heatsinks are currently still expensive, and usually recommended for very compact builds where a standard ‘stack’ heatsink won’t fit. But they will mount the same way as any other heatsink, as long as your CPU and board layout are supported.

Shopping

When you’re shopping for a heatsink there are three aspects that must be addressed:

  1. TDP. Simply put: The expected heat output of your CPU.
  2. Heat Spikes. How much difference in heat output between Idle, and full load.
  3. Physical space. You can go buy THE BEST COOLER EVER, and it’s not going to help if it won’t fit on your board or in your case.

Specifics

We’ll first address TDP. Generally speaking, the more powerful your CPU, the more heat it will put out under load. So if you’ve built a low-power office PC with a Ryzen 3, you won’t need a massive cooler. If you’re building the ultimate gaming PC, or a video rendering box, you will need to invest in a high performance heatsink. And of course if you’re doing ANY overclocking, that will increase your thermal needs regardless of your starting point.

Heat spikes happen in the time between going from no CPU activity to full load. On an inadequate cooler a heat spike will be very sharp, which is not good for your CPU. The better the cooler, the less intense the spikes will be and the less risk to the chip.

If you have a good cooler and are still experiencing sharp spikes, take a look at the rest of the PC. There’s a chance you have a bad mount on the cooler, or simply inadequate airflow through the case itself.

Lastly there’s physical space to account for. The less space you have in your PC, the more valuable it is to the cooling situation. A mid-tower will usually be plenty wide enough for the average ‘stack’ style cooler. But depending on the layout, other internal components may get in the way of an especially thick heatsink.

Conversely, an ultra compact PC will usually come with a specifically designed cooler that will fit, but may not remove heat as effectively as you’d like. And if you’re building a compact PC from scratch you need to find the optimal solution yourself.

Decisions, decisions…

So then how do I choose? I recommend looking at every heatsink available on whatever site or store you’re shopping at. Don’t ignore the customer reviews either, the good and the bad. You should make sure to read all the available information, especially the physical dimensions. Even if the TDP isn’t listed, you can usually roughly calculate it using the number of heatpipes and surface area of the fins.

CPU cooler comparison T2 vs T4
My old cooler on the left, and my new cooler on the right. Old one is rated for 95W TDP, and barely cooled my FX 6300.

Using my own experience as a baseline, the Segotep T2 is rated at 95W TDP. The FX 6300 CPU is rated to put out 95W TDP on stock settings. The T2 cooled it adequately at stock settings, but that was the ceiling of its capacity.

The Coolermaster Hyper T4 doesn’t actually list a TDP rating, but we can rough it out. With double the number of heatpipes, and at least double the fin real estate, I estimated 40 W more TDP. The results of my actual use supported this. It’s also a good example that double the heatsink doesn’t necessarily mean double the dissipation. There is a curve of diminishing results.

With this significantly better cooler, and double the heatpipes, my spikes smoothed out very nicely. I overclocked the CPU to 4.09 Ghz, and retained the nice smooth heatspike curve, proving the quality of the new heatsink.

Physical size, however, is an interesting conundrum. Because of how large the Hyper T4 is, I had to rearrange certain wires, and remove my RAM cooler to make it fit. Of course this isn’t going to matter at all if the one you bought doesn’t fit your CPU. Be sure to check the compatibility list as well.

Thermal Interface Material, AKA Goop

Once you’ve done the maths and chosen a heatsink, you need one last thing: TIM. Thermal Interface Material is the paste, pad, or gel that goes between the CPU and the heatsink. Colloquially known as ‘thermal goop’, this class of material fills the miniscule spaces between the CPU and heatsink, making it easier to pass heat from one to the other.

There are many different kinds, types and brands of the stuff. Choosing one depends on the type of scenario you’re aiming for. Most people will not notice a significant difference between brands. That said, a goop of significantly lower quality will have a noticeable negative impact on cooling performance.

Also, assuming this is your first time installing a heatsink, you don’t need to buy much. Most heatsinks will include a little packet of the stuff in the box, but most professionals will eschew it in favour of their preferred substance.

If you’re just replacing a heatsink in an office PC with no special intention, the little packet will be good enough. But if you’re building a high performance PC, you should invest in a better goop. Additionally if you ever get into sub-zero cooling with compressed freon or TEC rigs, there are special low-temp TIMs available.

The shopping process for TIM is the same as the heatsinks. Look at all of them, read the specs, and especially for first timers, read customer reviews. A goop with consistently good or consistently bad reviews can usually be relied upon to be exactly what you expect.

Once you’ve got the cooler and the TIM in hand, the rest is easy!

Follow the instructions, go slow, and if something isn’t fitting, just take it out and try again. Unlike the early 2000s, most CPU mounting hardware is interchangeable. And for the few that aren’t, heatsink manufacturers include a pile of adaptors in the box.

You are ready! Assuming you understood and followed this guide, you’ve got the solution you need. Enjoy your new thermal paradise!